1. Field of the Invention
This invention generally relates to laser scanner systems for reading indicia of different light reflectivity such as bar code symbols and, more particularly, to so-called mirrorless scanner systems wherein system components, other than mirrors, are employed to effect sweeping or scanning of symbols to be read.
2. Description of Related Art
Laser scanner systems and components of the type exemplified by U.S. Pat. Nos. 4,251,798; 4,360,798; 4,369,361; 4,387,297; 4,593,186; 4,496,831; 4,409,470; 4,460,120; 4,607,156; 4,736,095; 4,758,717; 4,816,660; 4,808,804; 4,816,661; 4,760,248; 4,871,904; 4,806,742; 4,845,350, 4,673,803; as well as U.S. application Ser. Nos. 148,669 and 147,708 all of said patents and patent applications being owned by the assignee of the instant invention and being incorporated by reference herein--have generally been designed to read indicia having parts of different light reflectivity, e.g. bar code symbols, particularly of the Universal Product Code (UPC) type, at a certain working or reading distance from a hand-held or stationary scanner.
Typically, a light source such as a laser generates a light beam which is optically modified to form a beam spot of a certain size at the working distance and is directed by optical components along a light path toward a bar code symbol located in the vicinity of the working distance for reflection from the symbol. A photodetector having a field of view extending across and slightly past the symbol detects light of variable intensity reflected off the symbol and generates electrical signals indicative of the detected light. These electrical signals are decoded into data descriptive of the symbol. A scanning component is situated in the light path. The scanning component may either sweep the beam spot across the symbol and trace a scan line across and past the symbol, or scan the field of view of the photodetector, or do both.
In any case, the scanner typically includes a moving mirror. For example, U.S. Pat. No. 4,251,798 discloses a rotating polygon having a planar mirror at each side, each mirror tracing a scan line across the symbol. U.S. Pat. Nos. 4,387,297 and 4,409,470 both employ a planar mirror which is repetitively and reciprocally driven in alternate circumferential directions about a drive shaft on which the mirror is mounted. U.S. Pat. No. 4,816,668 discloses a multi-mirror construction composed of a generally concave mirror portion and a generally planar mirror portion, the multi-mirror construction being repetitively and reciprocally driven in alternate circumferential directions about a drive shaft on which the multi-mirror construction was mounted.
No matter what the shape or orientation of the mirror, the known scanning components employed in laser scanning systems moved mirrors to perform the aforementioned sweeping and scanning actions. Moving other laser scanning system components was not thought to be practical. Thus, moving a gas laser tube was unthinkable, particularly in hand-held, compact system applications, due to the large size and the requisite large room necessary to accommodate a moving gas laser tube. Moving an optical lens was also not thought to be desirable, because optical alignment is critical in laser scanning systems. Hence, it was the mirror that was typically designated to effect the sweeping/scanning functions. However, in some laser scanning applications, mirror movements have not been found to be altogether desirable.
In non-laser scanning systems of the type exemplified by U. S. Pat. No. 4,578,571, a non-laser light emitting diode, an optical assembly, a photodetector, and electronic preamplifier/filter circuitry are all fixedly mounted on a common support that is connected to a cantilevered bimorph which is reciprocatingly driven to jointly move all the aforementioned components back and forth over a bar code symbol to be scanned. The large volume and heavy mass of all the commonly-mounted non-laser system components requires the expenditure of a great deal of power for the drive. This is not altogether practical in those cases, e.g. battery-powered operation, where power consumption is to be held to a minimum. Also, moving only one or more non-mirrored system components relative to another for conserving power was heretofore not considered desirable, because of the optical alignment problems described above. One feature of this invention resides, briefly :stated, in a mirrorless scanner arrangement in a light scanning system for reading indicia having parts of different light reflectivity, e.g. bar code symbols having alternating bars and spaces. The system is of the general type which includes a light source component, e.g. a laser, for emitting a laser light beam; an optical component, e.g. a focusing lens and/or an aperture stop, for optically modifying and directing the laser beam along an optical path toward the symbol located in the vicinity of a reference plane exteriorly of the system; and a photodetector component, e.g. a photodiode, having a field of view and operative for detecting at least a portion of light of variable intensity along a return path reflected off the symbol, and for generating an electrical signal indicative of the detected light intensity. This electrical signal is thereupon processed and converted to data descriptive of the symbol.
In accordance with this invention, the mirrorless scanner arrangement includes means for mounting at least one of the components for repetitive, reciprocating movement relative to at least another of the components, as well as drive means for repetitively, reciprocatingly moving the mounting means and said at least one component to scan at least one of said light beam and said field of view. Only one or only two of said components can advantageously be reciprocated relative to said other components. In addition, all the components can be jointly reciprocated, in which event, it is advantageous if the optical and return paths are co-linear, at least within a housing in which all the aforementioned components are housed.
Advantageously, the drive means includes a motor having an elongated shaft, and operative for reciprocatingly turning the shaft about an axis which extends along the elongation of the shaft in alternate circumferential directions over arc lengths less than 360.degree., e.g. 10.degree. to either side of a center position. Said at least one component is mounted on the shaft for joint turning movement therewith.
The component mounted on the shaft may be the laser, e.g. a semiconductor laser diode, a focusing lens, an aperture stop, the combination of a focusing lens and-an aperture stop, or the entire combination of the diode, the lens and the aperture stop. Also, the photodiode could be mounted on the shaft for joint turning movement therewith. Since the diode requires a power supply, e.g. a 12-volt DC source, and since the electrical signal developed by the photodiode must be conveyed to signal processing circuitry, electrical coiled tensile wires are advantageously connected to the laser diode and the photodiode.
Rather than turning the aforementioned components about an axis, the drive means may also be operative to reciprocatingly move one or more of said components in a plane which is perpendicular to an optical axis along which the optical path extends in a center position. Such planar movement can be effected by many types of drives, e.g. an electromagnetic drive, a mechanical drive, a piezoelectric drive, and a bi-metallic heating drive.
The mirrorless scanner arrangement of this invention can be used to generate a single scan line over the symbol to be read, or can be used with other scanner components to generate a multi-line scan pattern over the symbol.
In addition, the mirrorless scanner arrangement is very compact in size and light in weight, and can be mounted in modular manner in many different system configurations. For example, the arrangement can be mounted in hand-held housings having any convenient shape, e.g. a gun-shaped head having a barrel and a handle, or a box-like head, or a cylindrical-type head, or in desk-top housings, e.g. a workstation having scan-above, scan-down, or scan-sideways capabilities, or in stationary system installations, e.g. mounted at a production line or at a cash register. The compact size and lightweight characteristic renders the arrangement very versatile for multiple applications and uses. The power requirements for reciprocating the one or more components to be reciprocated is minimal. Advantageously, the arrangement is easily removable from the system in which it is installed. An arrangement requiring replacement is easily interchangeable with another.